ACS711EX Quiescent Output Voltage

I was having a hard time getting reasonable current measurements with my setup so I removed everything and just hooked up a power supply to VCC and GND and used a multimeter to measure OUT. Should it be very close to VCC/2? I’m seeing values that drift enough to give significant measurement error.

For example when I supply 3.59 V to VCC I’m measuring 1.706 V at OUT with my multimeter, and at 5.33 V to VCC I’m measuring 2.74 V at OUT. So, clearly the quiescent output voltage is going in the right direction as I vary VCC, but it’s off by enough that I would be measuring around an amp of current even with nothing hooked up to IP+/IP-.

Is something wrong, or is this normal and something I just have to calibrate for?


What you are describing seems normal for those current sensors, though the offsets you are measuring might be a little worse than what is specified. Do you get reasonable results if you measure and subtract the offsets? How and where are you measuring the voltage of your Vcc supply?


I was measuring using a multimeter across the VCC and GND pins on the ACS711EX right before measuring across OUT and GND. I do get reasonable numbers if I use the measured OUT voltage with no current as my neutral point and calculate offsets from that.

I was writing up some sample code that others might use so if this was normal I’d need to include a calibration step vs. just telling them use particular values if they knew their supply voltage.

That sounds reasonable; we generally expect that people working with those sensors will need to calibrate to determine the offsets for their specific units.